Engine/Sparkplug issue (misfires)

[Nebular]

A few weeks ago I changed the sparkplugs on my 02 trailblazer. It turned out to be a bit of a disaster because I broke 2 of the bolts tightening/loosening it. By some miracle I got both of them out but was forced drive around with one of the plugs loose causing frequent problems with acceleration/check engine light. I recently bought and replaced the missing bolts, but the problem still occurs to some degree.



The symptoms are this:

Driving normally with my foot on the gas accelerating ill reach to about 50 and then the transmission (or engine?) will teeter and have problems getting into the next gear. The check engine light will also flash.This also used to occur around 30 mph before I got the new bolts in place. The car also trembles a bit more than usual on idol.



Any ideas? Perhaps the contact between the plugs and the sparkplug isn't good enough on one or two of them?

 

[The_Roadie]

Welcome. Pull the coils and reseat them with extreme care to be straight. Many folks have posted with symptoms like yours and the cause was putting the coils back on at an angle and the boots didn't snick down over the plugs properly. Or some conductive contamination on the boots.

 

[Nebular]

Thx for the reply. I plugged a read in and got P0303 "Cylinder 3 Misfire Detected. So I guess I'll give that coil a look when I get a day of good weather. Which one is cylinder 3? 3 down starting up or 3 up starting down?

 

[IllogicTC]

Starting at the front of the engine (the side toward the fan) is cylinder 1, with cylinder 6 rounding our count off at the rear next to the firewall. You're lucky it's 3, 2-4 are easy to maneuver and work with.

 

[Nebular]

Thanks for the response but what is the firewall?

 

[Too Fast]

The firewall is the wall between the engine compartment and the passenger compartment. So, cylinder number 6 is back farthest away from the fan on the engine.

 

[Nebular]

Got it. Thanks.

 

[Nebular]

*Update*

My reader read it was cylinder number 3. I took out the coil, removed spark plug to clean it. Also cleaned the spring inside the coil (simple mechanism) and placed it back. This resulted in the same symptoms; same reading.

Today I swapped coil 3 with coil 2 (so now the coil in question is in the 2nd cylinder, I made a mark on it to track it). As of right now it displays the same symptoms, however, the check engine light blinks but does not stay lit not allowing me to get a reading. I suppose this time I hope it reads misfire in cylinder 2 meaning that the coil in question is bad.

My questions now are: What if the check engine never stays lit? What if cylinder 3 continues to misfire?

 

[IllogicTC]

From what I understand Torque Pro has cylinder-specific misfire counters on it. That's around a $25-30 investment for another code reader, but with more functionality overall for the price range.

Or you could take it on down to a place with a Tech II, like a stealership.

And what do you mean by cleaning the spark plug? You didn't contact the electrode surface did you?

 

[Nebular]

What's that part of it? I cleaned the back end, the thread, and the porcelain.

 

[IllogicTC]

What's that part of it? I cleaned the back end, the thread, and the porcelain.

Sorry for the long delay in response. I generally hover around the 360/370/305 platform.

The electrode is the little dot in the center of the spark plug, on the half that goes into the block. Specifically I am referring to what is called the center electrode in the diagram below. Everything else is pretty well fair game for cleaning, but it's important to not touch the center electrode thanks to the platinum/iridium/etc they coat it in.

View attachment 33084

 

[Nebular]

No problem. I fixed this problem. It was indeed a bad coil.